Linear alpha-olefins are compounds having established utility in a variety of applications. For example, linear alpha-olefins having 8 to 20 carbon atoms are key feedstocks in the production of surfactants, plasticizers, synthetic lubricants and polyolefins. High purity alpha-olefins are particularly valuable in the production of low density polyethylene and in the oxo process.
The most successful processes for the production of alpha-olefins to date are those catalyzed by nickel complexes of phosphinecarboxylate ligands and sulfonated ylide/nickel type compounds. While these catalysts are quite active and have good selectivity insofar as the production of alpha-olefins is concerned, the art is continuously searching for olefin oligomerization catalysts which display higher activity and greater alpha-olefin selectivity and allow for a more economical process.
It is known in the prior art to prepare linear alpha-olefins by oligomerizing ethylene at elevated temperature and pressure in a reaction solvent containing a catalytic nickel complex. Particularly useful as catalysts for this process are the complexes prepared as the reaction product of an olefinic nickel compound and a bidentate ligand. Illustrative ethylene oligomerization processes employing a nickel complex catalyst are described in U.S. Pat. No. 3,676,523, U.S. Pat. No. 3,686,351, U.S. Pat. No. 3,737,475, U.S. Pat. No. 3,644,564, U.S. Pat. No. 3,647,914, U.S. Pat. No. 3,647,915, U.S. Pat. No. 3,825,615, U.S. Pat. No. 4,020,121, U.S. Pat. No. 4,260,844, U.S. Pat. No. 4,528,416, and U.S. Pat. No. 4,822,915.
It has now been found that catalysts prepared from a particular five coordinate phosphorus ligand precursor are particularly suitable as oligomerization catalysts. None of the foregoing references contains a catalyst prepared from a five coordinate phosphorus ligand precursor.